The purposes of the project are to determine the effects of abnormal glucose tolerance on outcome of the pregnancy, to determine long term prognosis for the women and their offspring, and to identify diabetes and impaired glucose tolerance during pregnancy in women in the Gila River Indian Community. By means of a glucose tolerance test as well as chart review, the diabetes status of every woman are determined at two-yearly intervals and during the third trimester of each pregnancy. Offspring are followed from age 5 years and the effects of the diabetic intrauterine environment are evaluated in conjunction with other risk factors for obesity and diabetes. To see if a woman~s weight at birth was a risk factor for diabetes during pregnancy, 642 Pima women (median age 22.9 years, range 15.2 to 34.9 years) were evaluated during pregnancy according to their birth weights. Rates of diabetes were 9.1 %, 1.8%, 3.0%, 2.2%, 6.5% and 23.1%, respectively, among those with birth weights of < 2.5, 2.5-3.0, 3.0-3.5, 3.5-4.0, 4.0-4.5, and greater than or equal to 4.5 kg (X2=20.5, df=5, p<0.001). Controlled by logistic regression for age, BMI and maternal diabetes during pregnancy in the previous generation, the rate of diabetes among the low birth weight women (<2.5 kg) was significantly higher than among the normal (2.5-4.0 kg) birth weight women (OR=6.01, 95% ci=1.15-31.4), and the rate among those who had been macrosomic (greater than or equal to 4.0 kg) at birth was also higher (OR=4.7, 95% ci=1.43-15.5). This association was stronger among the 15-24 year old women than among the 25-34 year old women. Low birth weight has been found to be a risk factor for diabetes in several populations, and in the Pima Indians, high birth weight is also a risk factor. In this study, both extremes of birth weight were associated with higher rates of diabetes during pregnancy, with the highest rates being found among those who had been most macrosomic (greater than or equal to 4.5 kg) at birth. Unlike the study in nonpregnant adults, during pregnancy a 2 to 3 fold higher rate was also found among those with moderate macrosomia (4.0-4.5 kg) at birth. This risk was not accounted for by diabetes during pregnancy in the previous generation, a strong risk factor in this population for diabetes in the offspring as well as a cause of macrosomia.